It's really quite simple. If it's a dog off the mark with what you have as far as diff ratio and tyre size change the diff ratio to something that improves the result.
Quicker take off will also mean higher RPM at highway speed. I.E: 100Klms at 2,100 RPM vs say 100Klms vs 2,400 RPM
As you stated you don't care about top end speed, but you should take into consideration highway RPM and fuel economy. If you just buzzing about town on the pose then 3.55:1 would be fine.